1. Field of the Invention
The invention relates to a machine for fitting and removing a tire from a rim of a wheel, comprising a frame, a table capable of attaching the rim thereto and of rotating said rim in a centered manner about an axis (Y), and a tool for fitting and removing the tire.
2. Prior Art
Such machines have been known for a long time and make it possible to fit and/or remove a tire from a rim, for example of a wheel of a motor vehicle or truck or motorcycle. To carry out this operation, the rim is first attached to the table so that its axis coincides with the axis of rotation of the table. Then the fitting/removal tool is brought over the rim in order to position it close to the edge of the rim. The tire is then removed and/or fitted in a known manner.
The known machines have hitherto proposed to bring the fitting/removal tool close to the edge of the rim according to two different types of mechanism.
According to a first type of mechanism, known for example from patent EP 1775148, the machine comprises a vertical column secured to the frame and a horizontal movable arm mounted so as to rotate about the axis of the vertical column. This movable arm has, at its distal end, a vertical bar at the end of which the tool is attached. Said vertical bar is mounted in vertical translation relative to the movable arm.
With such a mechanism, the tool can be brought close to the edge of the rim, first by making the horizontal arm pivot until the tool is level with the edge of the rim, and then by making the bar slide vertically until the tool is virtually in contact with the edge of the rim. The mechanism is then immobilized in this position before the tire is fitted or removed.
However, with such a mechanism, the overhang of the tool relative to the vertical column is relatively large. This has the drawback that the mechanism—and in particular the horizontal arm—will sustain relatively large deformations when the tire is fitted or removed from the rim, which risks causing a contact between the tool and the rim and thus damaging the rim. Moreover, following the pivoting of the horizontal arm, the azimuthal position of the tool relative to the rim will vary with the diameter of the rim so that, with such a mechanism, it is not possible to position the tool in an optimal manner for various diameters of rim.
These two problems are all the more marked if the difference between the largest and the smallest diameter of rim is great.
According to a second type of mechanism, known for example from patent EP 1593533, the machine comprises a vertical column secured to the frame and a horizontal movable arm mounted in translation perpendicularly to the vertical column and radially relative to the rim. This movable arm also has, at its distal end, a vertical bar at the end of which the tool is attached. Said vertical bar is mounted in vertical translation relative to the movable arm.
With such a mechanism, the tool can be brought close to the edge of the rim, first by making the horizontal arm slide until the tool is in line with the edge of the rim, and then by making the bar slide vertically until the tool is virtually in contact with the edge of the rim. The mechanism is then immobilized in this position before the tire is fitted or removed.
Therefore, with this second type of mechanism, the azimuthal position of the tool relative to the rim will not vary with the diameter of the rim to be treated.
However, apart from the sliding mechanism of the horizontal arm, a clearance will appear over time between the horizontal arm and the vertical column, thus causing a misalignment of the tool relative to the rim and a risk of contact with the latter.
Moreover, with such a mechanism, the overhang of the tool relative to the vertical column is also relatively great, and all the more so if the difference between the largest and the smallest diameter of rim is great. It therefore has, from this point of view, the same drawbacks as the first mechanism.